(1) Field of the Invention
The present invention relates to a heat-sensitive recording material that utilizes a color forming reaction between a leuco dye and a developer.
(2) Description of the Related Art
Heat-sensitive recording materials which utilize a color forming reaction between a leuco dye and a developer are relatively inexpensive and the required recording device is compact and easy to maintain, and therefore these materials are used in a wide range of fields, such as recording media for facsimile machines, word processors, various types of computers, and other such applications.
As the field of use of these heat-sensitive recording materials has expanded, the environments in which they are used have become increasingly severe. There is a need for a material that will simultaneously satisfy such requirements as good resistance of the non-recorded image portion to heat and light, good storage stability of the recorded image, and high-speed recording. So far, however, if the heat resistance and light resistance of the non-recorded image portion are improved, there has generally been a decrease in the storage stability of the recorded image and in recording sensitivity.
International Publication WO00/35679 discloses that a heat-sensitive recording material which makes use of N-p-toluenesulfonyl-Nxe2x80x2-3-(p-toluenesulfonyloxy)phenylurea as a developer is superior in terms of recording sensitivity, resistance of the recorded image to oil, water, plasticizers and so forth, and resistance to background fogging, and other properties, but no specific measurement data is given.
Unexamined Japanese Patent Publication No. 1996-216528 discloses a heat-sensitive recording material which makes use of 3- (N-ethyl-p-toluidino)-6-methyl-7-anilinofluoran as a leuco dye, and 4,4xe2x80x2-dihydroxydiphenyl-sulfone or 2,4xe2x80x2-dihydroxydiphenylsulfone as a developer, and states that this recording material has excellent recording sensitivity and undergoes less degree of background fogging in a high temperature environment at 100xc2x0 C., and has an excellent storage stability of the recorded image (with less decrease in recording density with a lapse of time).
Unexamined Japanese Patent Publication No. 1997-11620 discloses a heat-sensitive recording material which makes use of 3- (N-ethyl-p-toluidino)-6-methyl-7-anilinofluoran as a leuco dye and 4-hydroxy-4xe2x80x2-isopropoxydiphenylsulfone as a developer, and states that the recording material has excellent recording sensitivity, entails less decrease in the recording density of the recorded image in a high temperature environment of 80xc2x0 C., undergoes less degree of background fogging, and has excellent resistance of the recorded image to humidity and water.
Further, Unexamined Japanese Patent Publication No. 1999-291633 discloses a heat-sensitive recording material that makes use of 3-(N-ethyl-p-toluidino)-6-methyl-7-anilinofluoran or 3-(N-ethyl-p-toluidino)-6-methyl-7-(p-toluidino)fluoran as a leuco dye and bis(3-allyl-4-hydroxyphenyl)sulfone as a developer, and states that the recording material is excellent in recording sensitivity, heat resistance (in a high temperature environment of 80xc2x0 C.), humidity resistance, plasticizer resistance, water resistance and light resistance.
While these known heat-sensitive recording materials have the respective properties listed above, there is still a need for a heat-sensitive recording material with even better properties, and particularly a heat-sensitive recording material that is excellent in recording sensitivity, heat resistance in an environment of 90 to 100xc2x0 C., light resistance, water resistance, plasticizer resistance, and so forth.
An object of the present invention is to provide a heat-sensitive recording material which has excellent properties such as recording sensitivity, heat resistance, light resistance, water resistance, plasticizer resistance and the like.
In a heat-sensitive recording material comprising a support and as formed thereon a heat-sensitive recording layer containing a leuco dye and a developer, the present invention uses, as one means for achieving the above object, N-p-toluenesulfonyl-Nxe2x80x2-3-(p-toluenesulfonyloxy)-phenylurea as the developer and the heat-sensitive recording layer contains at least one fluoran-based leuco dye having a melting point of 190 to 230xc2x0 C. and/or at least one pigment selected from the group consisting of aluminum hydroxide, amorphous silica, kaolin and talc.
Specifically, the present invention provides the following heat-sensitive recording materials.
1. A heat-sensitive recording material comprising a support and a heat-sensitive recording layer formed on the support and containing a leuco dye and a developer,
the developer being N-p-toluenesulfonyl-Nxe2x80x2-3-(p-toluenesulfonyloxy)phenylurea, and
the heat-sensitive recording layer containing (a) at least one fluoran-based leuco dye having a melting point of 190 to 230xc2x0 C. and/or (b) at least one pigment selected from the group consisting of aluminum hydroxide, amorphous silica, kaolin and talc.
2. The heat-sensitive recording material according to Item 1, wherein the heat-sensitive recording layer contains N-p-toluenesulfonyl-Nxe2x80x2-3-(p-toluene-sulfonyloxy)phenylurea as the developer and (a) at least one fluoran-based leuco dye with a melting point of 190 to 230xc2x0 C. and (b) at least one pigment selected from the group consisting of aluminum hydroxide, amorphous silica, kaolin and talc.
3. The heat-sensitive recording material according to Item 2, wherein the fluoran-based leuco dye with a melting point of 190 to 230xc2x0 C. is 3-(N-ethyl-p-toluidino)-6-methyl-7-anilinofluoran.
4. The heat-sensitive recording material according to Item 2, wherein the fluoran-based leuco dye with a melting point of 190 to 230xc2x0 C. is 3-(N-ethyl-p-toluidino)-6-methyl-7-anilinofluoran and the pigment is aluminum hydroxide.
5. The heat-sensitive recording material according to Item 2, wherein the heat-sensitive recording layer further contains a sensitizer.
6. The heat-sensitive recording material according to Item 5, wherein the sensitizer is at least one member selected from the group consisting of 2-naphthyl benzyl ether, 1,2-di(3-methylphenoxy)ethane and 1,2-diphenoxyethane.
7. The heat-sensitive recording material according to Item 1, wherein the heat-sensitive recording layer contains N-p-toluenesulfonyl-Nxe2x80x2-3-(p-toluene-sulfonyloxy)phenylurea as the developer and (b) at least one pigment selected from the group consisting of aluminum hydroxide, amorphous silica, kaolin and talc.
8. The heat-sensitive recording material according to Item 7, wherein the heat-sensitive recording layer contains a fluoran-based leuco dye with a melting point under 190xc2x0 C.
9. The heat-sensitive recording material according to Item 7, wherein the pigment is aluminum hydroxide.
10. The heat-sensitive recording material according to Item 7, wherein the heat-sensitive recording layer further contains a sensitizer.
11. The heat-sensitive recording material according to Item 10, wherein the sensitizer is at least one member selected from the group consisting of 2-naphthyl benzyl ether, 1,2-di(3-methylphenoxy)ethane and 1,2-diphenoxyethane.
12. The heat-sensitive recording material according to Item 1, wherein the heat-sensitive recording layer contains N-p-toluenesulfonyl-Nxe2x80x2-3-(p-toluene-sulfonyloxy)phenylurea as the developer and (a) at least one fluoran-based leuco dye with a melting point of 190 to 230xc2x0 C.
13. The heat-sensitive recording material according to Item 12, wherein the fluoran-based leuco dye with a melting point of 190 to 230xc2x0 C. is 3-(N-ethyl-p-toluidino)-6-methyl-7-anilinofluoran.
14. The heat-sensitive recording material according to Item 12, wherein the heat-sensitive recording layer further contains a sensitizer.
15. The heat-sensitive recording material according to Item 14, wherein the sensitizer is at least one member selected from the group consisting of 2-naphthyl benzyl ether, 1,2-di(3-methylphenoxy)ethane and 1,2-diphenoxyethane.
16. The heat-sensitive recording material according to Item 1, which further comprises, between the support and the heat-sensitive recording layer, an undercoat layer comprising as the main components a binder and at least one member selected from the group consisting of (i) an oil-absorbing pigment with an oil absorption (according to JIS K 5101) of at least 70 ml/100 g and (ii) organic hollow particles.
17. The heat-sensitive recording material according to Item 1, which further comprises, on the heat-sensitive recording layer, a protective layer comprising as the main components a binder which has a film-forming ability and, if desired, a pigment.
18. The heat-sensitive recording material according to Item 16, which further comprises, on the heat-sensitive recording layer, a protective layer comprising as the main components a binder which has a film-forming ability and, if desired, a pigment.